Inductive components

ABSTRACT

An inductive component having a central core comprises two stacks of U-shaped laminations disposed side by side so that the adjacent limbs constitute the central core. The outer limbs of the two stacks are bent towards the central core with the laminations at the ends of the outer limbs parallel to those of the central core.

United States Patent 11191 Koh Nov. 27, 197-3 [54] INDUCTWE COMPONENTS FOREIGN PATENTS 0R APPLICATlONS Inventor! Q s K J00 ChialTeh 611,942 10/1960' 11a1 336/212 Smgapore C1ty, Smgapore 258,348 5/1963 Austra 1a 336/83 1,337,426 8/1963 France 3361215 [22] 1972 956,319 4/1964 01661131116111 336/212 [21] Appl. No.: 278,126

Primary ExaminerThomas .l. Kozma 52 US. (:1 336/160, 336/212, 336/217, Hlman et 336/234 51 1111. c1. ..11011 27/24 1 ABSTRAFT [58] Field of Search 336/160, 212, 234, An mductlve P havmg a central Core 336/214, 215, 216 217 83 prises two stacks of U-shap'ed laminations disposed side by side so that the adjacent limbs constitute the [56] References Cited central core. The outer limbs of the two stacks are bent towards the central core with the laminations at UNITED STATES PATENTS the ends of the outer limbs parallel to those of the 2,548,624 4/1951 $612161 336 212 central core 2,634,321 4 1953 Larkin 336/217X 3,289,280 12 1966 Jones 336 160 x I 6,Cl aims,4D rawi'ng Figures e 1 a I INDUCTIVE COMPONENTS BACKGROUND OF THE" INvENT oN This invention relates to inductive components having cores, such as reactors or chokes, and transformers, such as power transformers or stray-field transformers.

A stray-field transformer is arranged to have a magnetic circuit with substantial leakage. Such transform: ers are often used fgr energising tiischarge lamps and have the advantage that the primary current is limited should the secondary winding be short-circuited. This limitation of the current is due to the high inductive impedance caused bythe magnetic leakage. One known type of choke or reactorhas two stacks of E-shaped laminations with corresponding lirnbs of the laminations end to end. A winding is wound around the central core formed by the central limbs of the two stacks of E-shaped laminations. In another lgnown construction, two stacks of U-shaped laminations are placed with their limbs end to end and ,a winding is fitted around one or both of the limbs of the thereby corn- :pletedrnag netic circuit. These constructions have the disadvantage that they require different blanking tools and dies for cutting laminations for difierent shapes and sizes of cores. A certain proportion of material has to be wasted in cutting the laminations using the blanking process.

SUMMARY OF THE INVENTION According to this invention, there .is provided aninductive component having a core comprising two stacks of U-shaped laminations disposed side by side so that the adjacent limbs constitute a central core, the outer limbsof the stacks of laminations being bent towards the central core so as to rest against the central core.

In one known core construction fora power or strayfield transformer, there is provided a stack of U-shaped laminations with a central stack of flat laminations resting against the base of the U-shapedlaminations. The ends of the U-shaped laminations are bent to engage the outer end of the central stacker are connected thereto by furher laminations. This known construction has the disadvantage that there is a joint in the magnetic circuit in the base of the stack of U-shaped laminations and the central stack where undeirablemagnetic losses always occur because it is efiectively impossible to produce the base of theU-shapedlaminations with a sufficiently flat surface so thatthecentral stack can be placed on it without anairgap, A transformer of any type having a core in accordance with this invention does not suffer fromthis disadvantage as the central stack is effectively integral withthe rest of the magnetic circuit.

A further advantage of a transformer. employin gia core in accordance with this inventionisthat it ispossi- .ble to use laminations of grain-orientated steel which allows magnetic flux to pass more easily in the direction cfgrain-orientation. In the known construction previously described it is impossible to utilise grainorientated steelbecause of the extremely low. permeabi ty wh h ould oc at th iointbetween he ba of the s ck of ape mina isn and the central stack. However it grainaorientated steelis used for. the laminations of a core of a transformer inaccordance with this invention, iris necessary to provide caps of bent-over laminations to connect magnetically the outer limbs of the stacks of U-shaped laminations to the central core because of the use of grain-orientated steel there will be low permeability therebetween even if they engage.

Preferably the outer limbs of the stacks of laminations are bent so thatthe laminations at the ends of the outer limbsare parallel to those of the central core.

It is preferred that the laminations are of grain orientated steel and that the component comprises two further stacks of U-shaped laminations,=the ends of the limbs of each further stack being disposedin line with and inhengagement with corresponding limbs of an individual one of the first mentionedstacks.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of this invention will now be described, by way of example only,.with' reference to the accompanying drawings of which each of FIGS. 1 to 4 is a sectional elevation through'a core of a transformer in accordance with this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, there are provided two adjacent stacks of generally U-shaped laminations l and 2 of a suitable magnetic steel, the two limbs 3 and 4 of the stacks l and 2 respectively being in contact. The outer limbs 5 and 6 of the stacks of laminations 1 and 2 respectively are bent inwardly in generally Z-formations to rest against the central core formed by the limbs 3 and 4. It will be appreciated that two complete magnetic circuits are formed by-the stacks] and 2. respec-' tively. The winding is mounted on the central core be fore the upper ends of the limbs 5 and 6 are bent into Z-formations as shown. n i

In the embodiment shown-in FIG. 2, the stacks 1 and 2 are similar to those shown in FIG. 1 but areof grainorientated steel so that the magnetic circuits are not completed at the upper ends of the limbs 3, 4, 5 and 6 by thefact that the limbs 3 and 5 and the limbs 4 and 6 respectively are in contact. In order to complete the magnetic circuit two stacks or caps 7 and 8 of U- shaped laminations are provided and complete the magnetic circuits of the limbs 3 and 5 and 4 and.6 respectively. As shown in FIG. 2, the ends of the laminations of .thelimbs 3, 4, 5 and 6 and the stacks 7 and 18 are v lternately of different lengths so that the laminations ofthe stacks or caps 7 and 8 can be fitted into the ends of thelaminations of the limbs 3 and 4 and 4 and 6,respectively. so as to reduce still further the effective air gap between the stacks or Caps 7 and -8 and the stacksl and 2respectively.

The embodimentshown in FIG.-3 is similar to that shown in FIG. 1 with the addition that the limbs 3 and 5 andthe limbs4 and 6 are joined at their mid-points by stacks of laminations 9 and 10 respectively which 1. An inductive component having a core comprisfirst and second stacks of U-shaped laminations com posed of grain-oriented steel and disposed side by side so that one limb of one of said stacks is placed adjacent one limb of the other one of said stacks to define a central core of said inductive component, the remaining outer limbs of each one of said stacks being bent towards said central core so as to rest thereagainst;

third and fourth stacks of U-shaped laminations of grain-orientated steel having limbs which are disposed in line with corresponding limbs of said first and second stacksrespectively, the ends of each of said limbs of said third and fourth stacks being in engagement with the ends of said corresponding limbs of said first and second stacks.

2. An inductive component as claimed in claim 1, wherein said remaining limbs of said stacks of laminations are bent so that the laminations at the ends of said remaining limbs are parallel to those of said central 4. An inductive component a s iclaimed in claim 1,

wherein further laminations extend between intermediate points on the limbs of at least one stack of said first and second stacks.

5. An inductive component as claimed in claim 4 wherein said further laminations are parallel to the laminations of the limbs at those points.

6. An inductive component as claimed in claim 4 wherein said further laminations are normal to the laminations of the limbs at those points. 

1. An inductive component having a core comprising: first and second stacks of U-shaped laminations composed of grain-oriented steel and disposed side by side so that one limb of one of said stacks is placed adjacent one limb of the other one of said stacks to define a central core of said inductive component, the remaining outer limbs of each one of said stacks being bent towards said central core so as to rest thereagainst; third and fourth stacks of U-shaped laminations of grainorientated steel having limbs which are disposed in Line with corresponding limbs of said first and second stacks respectively, the ends of each of said limbs of said third and fourth stacks being in engagement with the ends of said corresponding limbs of said first and second stacks.
 2. An inductive component as claimed in claim 1, wherein said remaining limbs of said stacks of laminations are bent so that the laminations at the ends of said remaining limbs are parallel to those of said central core.
 3. An inductive component as claimed in claim 1, wherein the laminations at the ends of said first, second, third and fourth stacks are alternately of different lengths so that projecting laminations formed at the ends of the limbs of each of said third and fourth stacks extend between projecting laminations formed at the ends of said corresponding limbs of said first and second stacks.
 4. An inductive component as claimed in claim 1, wherein further laminations extend between intermediate points on the limbs of at least one stack of said first and second stacks.
 5. An inductive component as claimed in claim 4 wherein said further laminations are parallel to the laminations of the limbs at those points.
 6. An inductive component as claimed in claim 4 wherein said further laminations are normal to the laminations of the limbs at those points. 